Politics, prophecy and cryptic text:   

Atto of Vercelli's Perpendiculum 

Giacomo Vignodelli 

 

 

1. The Polipticum quod appellatur Perpendiculum by Atto, Bishop of Vercelli 

between 924 and 960, is a well-known source for anyone who studies the 

history of the Italic kingdom in the post-Carolingian period, for those studying 

the history of political thought in the Middle Ages and, perhaps to an even 

greater extent, for Middle-Latin philologists. However, the reasons for its fame 

lie in its singular characteristics of composition, in the obscurity of its contents 

and particularity of its tradition: because of its very fame of being an almost 

unsolvable enigma, it has long remained on the margins of historical and 

philological research. 

The text is preserved in a single manuscript, which Atto himself had prepared 

within the scriptorium of the cathedral in Vercelli and which can now be found 

in the Apostolic Vatican Library (it is the Vaticano Latino 4322). The 

manuscript, which makes up a compilation of the Bishop’s works, contains 

the text of the Perpendiculum in two different versions, copied one after the 

other and both preceded by Atto’s monogram: the first is a draft “coded” in the 

scinderatio technique (which, as is known, consists in arbitrary shifting of 

terms within the sentence so as to create an artificial order incomprehensible 

on a first reading) a draft “coded”, I said, adopting the scinderatio technique 

and using obsolete words, or obsolete meanings of common terms.

 

This first draft is followed by a second version which represents a partial de-

coding: the word order is put in place, numerous interlinear annotations 

provide flat synonyms of the strange terms utilized by the Bishop and almost 

as many notes on the margins provide an explanation to many obscure 

points. 

However, rather than the singular form given to it by its author, and only 

partially de-codified in this self-commentary, it is the contents of the text 

which raise the most questions: in the first half of the work the Bishop 

recounts, through a long series of obscure allusions, the struggle for control 

of the kingdom fought between legitimate kings, usurper kings and members 

of the aristocracy of various ranks, yet without ever naming anyone or making 

any specific reference. This intricate account of plots and mutual betrayals is 

followed by a theoretical reflection difficult to interpret, which takes up the 

second half of the work. 

What complicates the picture is the existence of a preface letter, at the 

beginning of both versions, which is also “coded” and has extremely 

enigmatic contents; in this preface, the author dedicates his writing to an 

unknown recipient. In sending this text, Atto explicitly asks the anonymous 

interlocutor for an answer concerning the problem debated in this work of his.

 

What I would like to present today are the results of the research that I carried 

out on this source: in fact, this text was the subject of my doctorate 

dissertation, as well as of its re-elaboration as a monograph published by the 

“Centro di Studi di Spoleto” in 2011. 

The aim of my research is to answer the basic questions on this source which 

are still unsolved, that is: what is the Perpendiculum? Under what 

circumstances and why was it written? Why did its author write it in a cryptic 

form? And finally, who is the anonymous recipient of the work, if that is 

possible to determine? 

2. As the questions raised by the preface letter and the particular double 

version laid out by Atto appeared to be too obscure if tackled by themselves, I 

felt it would be better to start simply from the text of the source: the 

comprehension of the rhetorical structure chosen by the Bishop in the 

composition of the work, technically of the dispositio which he wished to lend 

to his writing, can in fact provide an answer to the first of our questions: what 

in fact is the Perpendiculum? 

If its rhetorical structure is analyzed, Atto’s work has a very clear composition: 

the two halves of the written text that I have referred to, divided also 

graphically into the Vatican codex, may be once again subdivided into two 

parts each: thus the text is made up of four sections. 

In the introduction the Bishop announces the subject and the aim of his 

writing; this if followed by the “narrative” part, or that long series of allusions 

to the political struggle in the kingdom. There is then a third block consisting 

of a theoretical treatise

 

based on examples from the Bible and drawn from 

ancient history followed (as a fourth part) by the exhorting conclusion 

crowned by a prayer for the protection of the kings. This simple layout 

corresponds perfectly to the quattuor partes orationis, the four parts of an 

oratio, envisaged by the classical rhetorical precepts filtered through the High 

Medieval tradition and in particular in the form of the oration suggested by 

Isidore of Seville in the Etymologiae. The text by Isidore in this case not only 

represents a generic source as, moreover, for all the scholarship of the High 

Middle Ages, but is the precise literal source of most of the annotations 

brought to the very text by Atto. So the four parts of the Perpendiculum 

correspond perfectly to the exordium –  narratio – argumentatio – conclusio. 

And they make Atto’s writing an oration, in a technical sense, a plea written to 

convince an audience and, in this case, the readers of a thesis on a political 

subject, a civilis quaestio.  

 

3. So what is the aim of the bishop’s complicated appeal? The thesis put 

forward by Atto may be summed up as follows: causing the usurpation of a 

throne already legitimately held by a king always constitutes not just a moral 

wrongdoing but also a political mistake, even if the king who is going to be 

ousted does not correspond fully to the ideal of a Christian king. Whoever 

conspires against his own legitimate king and calls against him a foreign king 

so that he may take up the crown, does not only decree his own damnation 

but also inexorably determines his own political downfall. In fact, according to 

the Bishop, even admitting that the subversive plot comes to fruition, the 

conspirators will have to be swept away by the political consequences of the 

ousting while the kingdom will fall into chaos. In order to convince the 

interlocutor of his own thesis, Atto recalls in the narratio (the narrative section 

of the oration), in a veiled way but one clearly recognizable to the informed 

reader, the history of the Italic kingdom starting from the Twenties of the Xth 

century, with the aim of showing how a first ousting, that which brought Hugh 

of Provence (the real anti-hero of the text) to the Italic throne, was followed by 

the elimination of the conspirators who had summoned him and who thought 

that they had given themselves a puppet king. This first ousting led to the 

chaos in which, according to the Bishop of Vercelli, the kingdom still found 

itself in at the moment of his writing. 

In fact, the correct understanding of Atto’s allusions to the Italic political 

struggle enables us to recognize the events which unfolded from the 

Twenties to the Fifties in the Xth century and therefore to date the 

composition of the text at between the end of 952 and 960 (that is, between 

the return of Berengar II to the Italic throne and Atto’s death). The possibility 

of determining the Bishop’s allusive references depends on the correct 

understanding of the source’s rhetorical structure, but it is made possible 

above all by the furthering of our knowledge of political history of the Italic 

kingdom in the Xth century which, both as regards its workings as well as its 

protagonists (that is, the ranks of aristocracy), has been at the centre of a 

cohesive season of investigations by Italian historiography during the last 

thirty years. 

The source in this context clearly shows its own direct political aim: to 

forestall the second coming of Otto I to Italy, trying to convince the 

interlocutor and other likely recipients of the text not to betray Berengar II, a 

king who, according to Atto, was perhaps unjust, but legitimate. 

The harsh criticism of the Bishop not only of the pro-Ottonian party but also of 

Berengar himself and of many protagonists of Italic politics contemporary to 

him, explains at least partly the need to cipher the contents of his own appeal 

and to avoid outspokenly naming the characters whose wrongdoings he 

analyses in the text. 

However, more than the worry of not exposing himself to dangerous enmities, 

it is the very layout of the narratio which requires such an attitude. In the 

words of Isidore of Seville: narratio  res gestas explicat: the section of the 

oration called “narration” explains the facts (pertinent to the political issue 

dealt with). Therefore, Atto does not refer fully to the events pertinent to the 

power struggle but concentrates on explaining the dynamics which 

determined them. Moreover, as the driving force of all the events is the 

eternal thirst for the worldly vainglory of men, naming the protagonists of past 

events does not matter much because in the future these same wrong 

decisions will be followed inevitably by the same negative consequences. The 

dynamics presented in the narration may refer to events which have already 

happened, and in fact these are described by the Bishop in such a way that 

they are easily understandable to the reader, but these same dynamics will 

repeat themselves inexorably in the future if Atto’s appeal is not heard. 

The analysis of the workings of the political struggle carried out by the Bishop 

of Vercelli makes the source even more interesting to our eyes: not only do 

we find ourselves up against one of the rarest preserved anti-Ottonian 

sources, thus a text which interprets the events of the mid-Xth century in a 

totally different way from other contemporaneous sources (and I am naturally 

referring first and foremost to Liudprand of Cremona), but it gives us what we 

could call an “inside” explanation of the workings of the power struggle: Atto 

was in fact one of the political protagonists of his time (particularly during the 

reign of Lothar II and Berengar himself). The Bishop concentrates particularly 

on the great turnover in the ranks of the aristocracy in the kingdom which 

came about in the second quarter of the Xth century, a turnover presented by 

Atto as a true catastrophe and not a minor cause of the chaos which the 

kingdom suffers from. 

 

 

4. But why did Atto want to make his own appeal in a cryptic form? The 

answer to this question goes beyond the political contingencies which 

certainly discourage the author from broadcasting the contents of his own 

work, even though this specific worry is witnessed by some rather patchy 

annotations in the manuscript, and is in line with the traditional aim of the 

scinderatio technique: that is, to make the text incomprehensible to any 

unwanted readers. Moreover, despite the fact that the elocutio contorta, a 

contorted arrangement of words, could be included in the highest rhetorical 

forms by his contemporary Rather of Verona who defines it as optima 

intelligentibus, excellent for those who can understand it, Atto’s choice of this 

register does not depend on a mere stylistic necessity. 

What leads us to the best explanation of the cryptic form adopted by the 

Bishop is the very title that he chose for his work. 

The double title of the source, Polipticum quod appellatur Perpendiculum, 

may be translated more or less as Complex Treatise called the Plumb-line, 

where this second term constitutes the proper name of the work, so to say. 

The plumb-line that the Bishop stretches out has a double meaning: on one 

hand, it is a positive tool to construct or reconstruct, on the correct 

foundations of legitimacy, the royal institution, so that the resulting 

construction is “true”, as opposed to the chaos inevitably generated by 

illegitimacy and usurpation. But, more than that, the work constitutes a clear-

cut prophetic warning, a reference to Chapter 34 of the Book of Isaiah, where 

the plumb line is held by God himself over Edom and represents inexorable 

divine judgment. 

Atto’s whole political discourse is in fact constructed on what we may define 

as episcopal prophetic teachings: the Bishop of Vercelli can correctly 

understand the past and future of the kingdom and indicate what he defines 

as the “way to get out of the Labyrinth” because he reads reality in the correct 

eschatological framework. The cause of the chaos which his contemporaries 

are experiencing is the blind search for worldly vainglory instead of the true 

glory of eternal salvation, and the consequences of this tragic inversion are 

the damnation of the powerful and chaos in the whole kingdom, over which 

looms future divine judgment. 

In this sense, the Bishop’s warning constitutes an example of a prophecy 

which must not come true. As with the case of Jonah’s preaching at Nineveh, 

the prophet warns the people as to what would happen if his words went 

unheard: his warning saves the city and the grim prediction of destruction 

does not come true, which does not mean that Jonah’s prophecy is any less 

“true”.  

Thus, alluding to Isaiah in the title, Atto suggests that unless the Italic 

magnates stop their plotting and abandon the path to vainglory, the worst 

outcome being the summoning of Otto I to Italy (because for the Bishop of 

Vercelli the only reason why he would be summoned would be to free the 

aristocracy of the yoke of Berengar, in a foolish project of making Otto a 

puppet-king or at least a king destined to be always absent from the 

peninsula), in short if the Italics do not listen to his appeal to them, what will 

happen is what Isaiah prophesized for the Edomites: beating down on the 

kingdom, divine judgment will cause Italy to become a desolate desert 

inhabited only by demons while thorns will grow in the abandoned palaces. 

This suggests us the reason why the Bishop adopted a cryptic form of writing: 

obscuritas/obscurity is the stylistic code of prophetic writing. 

Let it be clear: the Perpendiculum is not a strictly prophetic text, but its 

ciphered form does not just constitute a pure rhetorical colour or a simple 

cryptographic means: the Bishop of Vercelli’s political appeal deploys all the 

prophetic power of the episcopal teachings in understanding the sense of 

reality past and present and in the attempt to direct future political decisions. 

 

5. The chapter house library at Vercelli preserves a Xth century copy of the 

commentary on Isaiah by Haymo of Auxerre, a codex which I found only after 

completing my book: the codex contains numerous annotations which 

comment on different key terms that we find in Atto’s text. And this also 

includes the very title of the work: next to the passage in which Haymo 

indicates the correct way to interpret the “Plumb-line” in Isaiah 34, with 

Sententia Dei, Judgment of God, a note has been added Perpendiculum quid 

sit: “here it is said what the Perpendicular is”. 

The study of this manuscript together with other manuscripts owned by Atto 

and which still lie in the chapter house at Vercelli will constitute the first phase 

of the project for a critical edition of the Perpendiculum that I have just begun 

at Sismel in Florence. 

 

6. Finally, a word on the recipient of the text: in my book I added to the 

conclusion a hypothesis which seems possible to me: many aspects of the 

preface letter indicate, as the likely recipient of Atto’s complex appeal, Bishop 

Wido of Modena and abbot of Nonantola, arch-chancellor of Berengar II, and 

a key force in Italian politics in the mid Xth century. If that is the case, the text 

has not produced the desired effect: Wido is one of the Italic leaders who 

would gain most benefit from the coming of Otto, at least at the beginning. 

Ironically, an umpteenth about face for Wido saw the end of his political 

career and his exile in the kingdom of Germany, almost as if this fulfilled the 

prevision provided by Atto’s writing.  

 

7. To sum up: Bishop Atto’s Plumb-line must be considered as the 

interpretation by a bishop of late Carolingian culture of the classical model of 

political oration. At a time of extreme uncertainty for the future of the Italic 

kingdom, in the mid-Fifties of the tenth century, the Bishop of Vercelli writes in 

order to convince the Italic magnates not to summon Otto of Saxony over the 

Alps, and with his own political discourse makes a full claim to his guiding role 

as bishop through the labyrinth on earth, acting as a guide to lead the people 

out of Chaos. 

In interpreting in full the prophetic character of his own teachings, he 

elaborates his personal appeal in a cryptic form. A form intended by Atto as 

the summit of rhetorical technique and a sign in itself of the sheperd’s power 

to understand the Truth beneath the deceptive appearance of worldly glory. A 

cryptic form thus chosen because it is the most effective to take action in the 

world and to guide the political decisions of his contemporaries. The 

subsequent failure of the political plan upheld by the Bishop, which Atto was 

not able to witness as he had already died in 961, makes his complicated 

appeal an even more precious source in our eyes today.